Markarian’s Chain in Virgo and Coma Berenices:
This famous string of bright NGC galaxies earns every bit of its fame. It’s a breathtaking view. The group is in the “nearby” Virgo Cluster with distances ranging from 32 million ly to well over 100 million. Seven of the galaxies in the chain are moving together. M 84 was discovered not to be one of them, although dropping it from "the Chain" was just unthinkable. The IC and PGC galaxies observed around the Chain are in the same ballpark for distance but are smaller than their NGC companions and generally dimmer. Our local group of galaxies is being drawn toward the Virgo Cluster and is itself part of the greater Virgo Supercluster of galaxies. Each galaxy has its own story, but I found NGC 4022’s particularly interesting. It’s being warped and stripped of its star-making material not by interaction with a neighbor but by the “ram pressure” exerted by the Virgo Cluster itself. 4022 will eventually become a “jellyfish galaxy”, with a stream like tentacles being pushed away from the jellyfish’s bell. Here’s a brief article on that.
Stand by for a long report...
Observing: This combined observation took place over 3 separate nights, with clear skies and breezy conditions, resulting in good to excellent transparency and poor seeing. SQM readings ranged from 20.67 to 20.89. The first night located the brighter members of the Chain, with the subsequent nights devoted to locating and confirming the fainter ones. All the NGCs were easily nailed down, but some of the ICs and PGCs were double-checked to make sure they were seen in averted vision and not averted imagination. The FOVs are from the observations using the 21mm TV Ethos @ 145x. Details and at times galaxies themselves were observed using both the 13mm Ethos @ 235x and 8mm Ethos @ 381x. The sketch is a combination of those views.
Messiers M84 and M86 anchor the west end of the chain and are impossible to miss, looking like hi-beam headlights coming at you in the fog. Even so, AV helps to see the extent of the large halos. 86 is larger and slightly oval, whereas 84 is more circular. Both are of near-equal brightness with the nod going to 86. Both showed significant brightening to a central core and a brighter, non-stellar nucleus.
The NGC galaxies:
Between M84/M86 and slightly south sits 4387, marked by a bright star just to its north. The galaxy is a small oval smudge, close to 2:1, that brightens toward the center.
Further south is 4388, a long 4:1 slash with a brighter, elongated center and tapered halo ends.
4413 to the ESE of 4388 was a little stinker and the only NGC that required some time and AV to pick up. Photos show it to be a beautiful face-on barred spiral which explains the low SB. Slightly oval, it shows a subtle but unmistakable brightening towards the center.
4425 is to the NE and nearly a twin of 4388 except dimmer and about 75% of 4388’s size. Easily held directly once found, its extent and rather concentrated core were best seen in AV.
4402 sits to the north of M86 and took a bit of looking to nail down. Found in AV over time it could be held directly but only just. It’s an elongated smudge with no brightening at the center. Photos show a thick dust lane that obscures the core. Faint as it is, it nonetheless served well as a marker for two far more dim galaxies nearby. More on those later.
4435 and 4438, known as “The Eyes” are the next step up the chain to the east. The two are interacting and pulling material from each other. 4435 is perhaps a 2:1 oval with a clear, bright core. 4438 also displays a bright core, hence the nickname. About the same size as 4435, 4438 also shows distinct tidal tails off both ends of the galaxy which makes it appear much larger than its companion. The distortion got Halton Arp’s attention and is entered in his Catalog of Peculiar Galaxies as Arp 120.
Another, smaller pair of galaxies sits to the ENE of the “Eyes” about the same distance as the “Eyes” are from M86. Head east to bright HIP 60896 (mag. 9.4) then straight north to 4461, a 3:1 oval with a bright, elongated core. Just to the north is its interacting partner 4458. This galaxy’s core is as bright as its neighbor’s, but the halo is smaller and circular. A bright star makes a triangle with the two galaxies, with 4461’s long axis pointed right at it.
Next up the chain to the NE and crossing into Coma Berenices is the solitary galaxy 4473. An elliptical like a half-sized M86, the galaxy shows a greater overall brightness than the two previous galaxies without showing as distinct a core: the brightness extending into its halo more so than with 4461 and 4468.
Hop due north for the same distance as 4473 is from 4461 to find 4477 and the eastern anchor of the chain. Only slightly oval, 4477 has a distinct and bright core and is roughly the same size as 4473. Photos show a bright bar and complex ring structure but those were not seen. More aperture and/or darker skies might reveal the bar. 4477’s companion 4479 is a nearly featureless, round smudge best seen in AV, however it was held directly.
The IC galaxies:
Starting back at the west end of the Chain and to the south of M84 is IC 3303. This one is small and AV only. It did show a slight brightening towards the middle and an intermittent stellar nucleus.
IC 3349 is to the SW of NGC 4413, forming the far point of a shallow triangle extending from the NGC’s position. It showed as a featureless and tiny AV smudge.
IC 3363 is about the same distance from NGC 4413 as is IC 3349, and due east of the NGC. Spotting it was aided by its stellar nucleus that winked in and out. That was true for several of these fainter and tiny galaxies.
IC 3355, also listed in the Vorontsov-Velyaminov Catalogue of Interacting Galaxies (VV) is an irregular galaxy. Couldn’t find what it’s interacting with, however, and photos don’t show a companion. Very low SB, it presents as a short AV-only slash, oriented N-S. Locating it is helped by seeing it as the top point of a shallow triangle with The Eyes and M 86. Studying the starfield is a must. It sits in the western line of an isosceles triangle of dim stars pointing just east of north, closer to the point than the base. A threshold star at the northern tip winked in and out periodically.
Two IC galaxies – 3388 and 3393 – lurk SE of distorted NGC 4438 (the Weeping Eye, perhaps?). About half the span of the field of view in that direction is a line of 4 stars of varying brightness, the first and third stars from the north being the brightest. IC 3393 sits due north of the northernmost star in the line, and IC 3388 is due west of the fourth star. 3393 was seen a bit more easily being perhaps a touch larger and brighter of the two, and its stellar nucleus was seen first and consistently. 3388 was tougher to see and its stellar nucleus was intermittent. Both halos were AV only.
IC 3386, also cataloged as PGC 41007, is just to the west of the NGC pair of 4461/4458. That pair of galaxies forms the base of a triangle for which IC 3386 is the point to the west, near a bright marker star. Knowing the starfield places the galaxy at the western base point of an obtuse triangle with two stars. The point star of the triangle is brightest, whereas the other base star fades in and out. The 2:1 oval was AV-only but did have a stellar nucleus that winked out intermittently.
PGC galaxies:
PGC 40636 sits at the east point of an equilateral triangle with two stars, the northern tip of which points directly to NGC 4388. An AV-only circular and tiny smudge, it showed no detail.
NGC 4022 was the marker for the last two PGC galaxies – 40598 and 40548. Knowing the starfield is critical as both galaxies are tiny, AV smudges. 40598 sits to the NW of 4022 and is helped by an intermittent stellar nucleus. It’s the eastern point of an equilateral triangle with two brighter stars in a line to the west forming the base. 40548 is also a tiny, round and featureless AV smudge. It also forms a triangle with two stars in the same line, but the galaxy is the western point.
An enjoyable and absorbing observation, and personally a marker for observing and sketching two years on from the first time I saw this group. Although I have to say that after grubbing for and confirming the smaller, fainter members it was fun to step back and appreciate the brighter ones and remember why it’s called Markarian’s Chain.
Sketching: white pastel pencils and white pastel powder on Bachmore 92 lb. black multimedia paper. M86 was drawn with a #12 Filbert and M84 with a #2 mop. Both cores were laid down with a #2 round brush and the nuclei with a 12/0 mini angular. All others were drawn with either the mini angular or a 10/0 mini-Filbert. A #5 pointed brush helped with touchup, and a 20/0 mini fan brush did the same for M84 and M86
Go here for the full image in the gallery Go here for the full image in the gallery
Thanks for wading through all this!
-b
Edited by bphaneuf, 05 April 2024 - 10:59 AM.
